I've encountered the 'too good to be homemade' thing too, when being judged by a panel of celebrities. -_-' That's why we say about masquerades "It's always a crapshoot" because you can't control who's going to be judging, who you're competing against, or even whether your sound will work for sure. You just do your best, that's all you can do. And if you have a bad experience, tell them about it...and if it doesn't get fixed, then vote with your feet and go elsewhere.

Normally (in my experience) approaching the judges while you're onstage isn't cool, but it does depend on the contest.